The present invention relates to the field of electrochemical processing, and more particularly to an apparatus and method for improving electropolishing action by keeping gas bubbles, which can interfere with such polishing, away from a polishing electrode. The predominant current usage of the present inventive apparatus and method for improved electropolishing is in the in place polishing of pipes used in processing facilities.
It is known in the art to deposit and/or remove materials by passing an electric current through a fluid electrolyte which is in contact with a conductive electrode. Materials are exchanged between the electrolyte and the electrode depending upon the direction of current flow and the ionization of materials to be deposited on or removed from the electrode. Electroplating is a well known application of this general method. Electropolishing is also well known in the art. In the electropolishing process, irregularities and deposits on a surface are removed by causing such to be drawn into the electrolyte solution.
An example is the in place electrochemical polishing of a pipe. In such an example, a cathode is drawn through the pipe while an electrolyte solution is simultaneously pumped through the pipe. The pipe acts as an anode and is electrochemically polished in the process. Since the electrolyte solution must be continuously pumped through the pipe during the process, it is most practical to recirculate the solution.
In the prior art it has been customary to circulate the electrolyte solution through the pipe in a direction opposite to that in which the cathode is drawn through the pipe. Although it may not have been the primary intended advantage of this direction of flow, at least an incidental advantage is that such an arrangement tends to cause any bubbles formed at the cathode to be carried back to that part of the pipe which has already been polished. Such bubbles, when present in the area of the electrode, tend to prevent the electrolyte from coming into direct contact with the pipe and, therefore, interfere with the polishing process. A dam adapted to facilitate the flow of such bubbles away from the polishing area has been used successfully by the present inventor. However, this solution has not been entirely successful where the electrode is moving through generally vertical, or at least non-horizontal, sections of the pipe, wherein the bubbles tend to float upward toward the electrode.
It would be advantageous to have additional methods and/or means for moving gas bubbles away from the electrode during an in place pipe electropolishing operation.
Such methods and/or means would be useful by themselves and/or in combination with existing methods and means.
Accordingly, it is an object of the present invention to provide an apparatus and method for improving the polishing action of a pipe inner surface electropolishing system.
It is still another object of the present invention to provide an apparatus and method for moving bubbles away from the polishing area in a pipe electropolishing system.
It is yet another object of the present invention to provide an apparatus and method for removing bubbles from the cathode area in a pipe inner surface polishing system which can be used in conjunction with existing methods and apparatus.
It is still another object of the present invention to provide an apparatus and method for removing bubbles from the cathode area in a pipe inner surface polishing system which can be easily and inexpensively added to existing pipe electropolishing devices.
Briefly, a known embodiment of the present invention is an improved in place electropolishing apparatus for polishing the inner surface of a pipe. According to one described embodiment of the present invention, a cathode is drawn through a pipe while an electrolyte solution is moved through the pipe in a direction generally opposite to the direction of travel of the cathode. However, when the cathode is moving generally upward through a vertical or inclined portion of the pipe, the direction of flow of the electrolyte is reversed such that the electrolyte also flows upward in the pipe, thereby carrying bubbles, which would otherwise tend to be trapped in the electropolishing area, away from the cathode.
According to one embodiment of the present invention, it is desirable to know where within a pipe the electrode is at any given time during the processing process. This can be accomplished in a number of ways, including but not limited to methods and means specifically discussed herein. For example, the cable which pulls the cathode through the pipe could be encoded (e.g., with colored or magnetic markings, or the like) such that the position of the cathode can be generally determined by keeping track of how much cable has been pulled through. Another means would be to measure the resistance and/or capacitance between the cathode and a measuring electrode placed at the end of the pipe and/or at various points along the pipe. Other means for detecting the position of the cathode could rely upon the fact that there is a significant amount of heat generated at the location of the cathode during the electropolishing process. This heat can be detected by an infrared camera, by thermisters placed at specified locations along the pipe, or by marking the pipe at various locations and/or intervals with a heat sensitive crayon that changes color or melts when heated by the cathode.
An advantage of the present invention is that polishing is improved in at least some non-vertical sections of a pipe.
Another advantage of the present invention is that gas bubbles are removed away from the area of the cathode in an in place pipe polishing system.
A further advantage of the invention is that it can be used in conjunction with known methods and/or apparatus for moving the bubbles away from the electrode in an in place pipe electropolishing system.
Still another advantage of the invention is that existing in place pipe electropolishing devices can be easily and inexpensively modified to incorporate the inventive method and apparatus.
These and other objects and advantages of the present invention will become clear to those skilled in the art in view of the description of modes of carrying out the invention, and the industrial applicability thereof, as described herein and as illustrated in the several figures of the drawing. The objects and advantages listed are not an exhaustive list of all possible objects or advantages of the invention. Moreover, it will be possible to practice the invention even where one or more of the intended objects and/or advantages might be absent or not required in the application.
Further, those skilled in the art will recognize that various embodiments of the present invention may achieve one or more, but not necessarily all, of the above described objects and advantages. Accordingly, the listed objects and/or advantages are not considered to be essential elements of the present invention, and should not be construed as limitations.